Liquid moisture curable polyurethane adhesives for lamination and assembly

Abstract

This invention relates to polyurethane prepolymer containing adhesives that are liquid at room temperature and that do not phase separate under typical storage and use conditions and that can be cured by exposure to moisture or active hydrogen-containing curing agents. The polyurethane prepolymer adhesives exhibit surprisingly good adhesion to plastics such as fiberglass reinforced plastics (“FRP”).

What is claimed is: 
     
       1. A liquid polyurethane prepolymer adhesive composition comprising a reaction product obtained by reacting a stoichiometric excess of polymeric MDI with polyether polyol; at least one liquid paraffinic oil; and at least one aromatic oil different from the paraffinic oil, wherein the liquid paraffinic oil and the aromatic oil are present in a by weight ratio of 2:1 to 1:2, and wherein the polyurethane prepolymer adhesive is moisture curable, and in liquid form at 25° C. and free of solvent. 
     
     
       2. A liquid polyurethane prepolymer adhesive of  claim 1  wherein the polymeric MDI is present in an amount from 10 to 70% by weight. 
     
     
       3. A liquid polyurethane prepolymer adhesive of  claim 1  wherein the polyether polyol is present in an amount from 20 to 70% by weight. 
     
     
       4. A liquid polyurethane prepolymer adhesive of  claim 1  wherein the liquid paraffinic oil is a mineral oil. 
     
     
       5. A liquid polyurethane prepolymer adhesive of  claim 1  wherein the liquid paraffinic oil is present in an amount from 0.2 to 10% by weight. 
     
     
       6. A liquid polyurethane prepolymer adhesive of  claim 1  wherein the liquid paraffinic oil is present in an amount from 1 to 8% by weight. 
     
     
       7. A liquid polyurethane prepolymer adhesive of  claim 1  wherein the aromatic oil is present in an amount from 0.2 to 15% by weight. 
     
     
       8. A liquid polyurethane prepolymer adhesive of  claim 1  wherein the liquid paraffinic oil has the general molecular formula of CH 3 [CH 2 ] n CH 3 , wherein n=15 to 50% by weight. 
     
     
       9. A liquid polyurethane prepolymer adhesive of  claim 1  wherein the polyether polyol is polypropylene glycol. 
     
     
       10. A liquid polyurethane prepolymer adhesive of  claim 1  having a viscosity from 1000 cps to 25,000 cps. 
     
     
       11. A liquid polyurethane prepolymer of  claim 1 , wherein the liquid paraffinic oil and the aromatic oil are present in a weight ratio of about 1:1. 
     
     
       12. The polyurethane adhesive composition of  claim 1  wherein the aromatic oil is 100% aromatic hydrocarbons. 
     
     
       13. An assembly comprising a first substrate, a second substrate, and a liquid moisture curable polyurethane adhesive of  claim 1  between said first substrate and said second substrate. 
     
     
       14. The assembly of  claim 13 , wherein at least one of said first substrate or said second substrate is a low surface energy substrate. 
     
     
       15. An article comprising cured reaction products of the adhesive composition of  claim 1  disposed thereon. 
     
     
       16. Cured reaction products of the adhesive composition of  claim 1 . 
     
     
       17. A liquid, moisture curable adhesive composition including a polyurethane prepolymer, the prepolymer comprising a reaction product obtained by reacting 10 to 60% by weight of composition of polymeric MDI with 20 to 70% by weight of composition of polyether polyol, wherein there is a stoichiometric excess of NCO groups; 0.2 to 10% by weight of composition of at least one liquid paraffinic oil; and 0.2 to 15% by weight of composition of at least one aromatic oil different from the paraffinic oil, wherein the liquid paraffinic oil and the aromatic oil are present in a weight ratio of 2:1 to 1:2, and wherein the polyurethane prepolymer adhesive is in liquid form at 25° C. and free of solvent. 
     
     
       18. A liquid, moisture curable polyurethane prepolymer, the prepolymer comprising a reaction product obtained by reacting only 10 to 60% by weight of composition of polymeric MDI with 20 to 70% by weight of composition of polyether polyol, wherein there is a stoichiometric excess of NCO groups; 0.2 to 10% by weight of composition of at least one liquid paraffinic oil; and 0.2 to 15% by weight of composition of at least one aromatic oil different from the paraffinic oil, wherein the liquid paraffinic oil and the aromatic oil are present in a weight ratio of 2:1 to 1:2, and wherein the polyurethane prepolymer adhesive is in liquid form at 25° C. and free of solvent.